Combination gear hobber, chamfer/debur and shaver apparatus and method

ABSTRACT

An apparatus is provided for manufacturing a gear component. The apparatus includes a plurality of tooling stocks movable relative to a base. The tooling stocks function to retain a component, as well as operably driving a combination hob/shaver tool and a combination chamfer/debut tool. The apparatus reduces the number of machines required to complete the gear component as well as reducing the cycle time for complete component manufacture. In this way, a more efficient manufacturing system is provided, whereby capital investment and operational costs are reduced.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/339,514 now U.S. Pat. No. 6,757,949 filed on Jan. 9, 2003, whichclaims the benefit of U.S. Provisional Application Ser. No. 60/367,795,filed on Mar. 27, 2002. The disclosures of the above applications areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention generally relates to component manufacturemethods, machinery and tooling and more particularly to an improved gearmanufacture method, tooling and machinery.

BACKGROUND OF THE INVENTION

Mass production of components, such as gears and the like, typicallyincludes a series of machines integrally linked in a production line.Such machines may include cutters, grinders, shavers, heat treat and thelike. Generally, a raw component is loaded at the beginning of the lineand each machine performs a specific manufacturing process on the rawcomponent, ultimately producing a finished product. Each step of theprocess includes an associated cycle-time. The cycle-time is the amountof time it takes a particular machine to perform its process, includingloading and unloading of a component. The cycle-time translates directlyinto manufacturing costs and thus component price.

In addition to cycle-times, each machine has associated costs. Theinitial cost is the capital investment required to purchase the machine.Other costs are incurred throughout the life of the machine. Theseon-going costs include maintenance, replacement parts, general runningcosts (electricity, lubricant, etc.) and the like.

Gear hobbing is one of a variety of methods employed for manufacturinggears and is generally used in mass production for rough cutting teethin gear blanks. In gear hobbing, the cutting tool is termed a “hob”.Generally, hobs are cylindrical in shape and are greater in length thanin diameter. The cutting teeth of a hob extend radially from thecylindrical body and follow a helical path about the hob, along thelength of the hob. Hobbing is a continuous process in which the hob andgear blank rotate in timed relation to one another. The cutting actionis continuous in one direction until the gear is complete.

The hob is fed across the circumferential face of a gear blank at auniform rate. As the hob moves across the circumferential face of thegear blank, both the hob and the gear blank rotate about theirrespective axes. As the hob cuts the gear blank, tooth profilesgradually form within the circumferential face of the blank and theteeth gradually take shape across the gear face.

Accuracy and production requirements dictate the type of hob to be used.Hob types vary from single-thread to double-thread or more in multiple.A single-thread hob makes one revolution as the gear being cut rotatesthe angular distance of one tooth and one space. For example, forproducing a spur gear having 49 teeth, a single-thread hob rotates 49times for one revolution of the gear blank. Similarly, when using adouble-thread hob, the hob rotates 49 times for two revolutions of thegear blank. Multiple threads increase the rotational speed of the gearblank accordingly. However, certain limitations are inherent in usingmultiple-thread hobs.

The number of threads is a function of the intended purpose. Althoughnot efficient for mass production, single-thread hobs may be used forboth roughing and finishing. Multiple-thread hobs are commonly used forroughing. As a result of the multiplication effect of multiple-threadhobs, speed increases, thus providing savings in cycle-time. However,compared to single-thread hobs, multiple-thread hobs leave much largerfeed marks on the tooth profiles of the gear teeth. For example, using asingle-thread hob, each tooth of the hob cuts every tooth space in thegear blank. A double-thread hob contacts every other tooth space duringany single revolution of the gear blank.

Various feed directions of the hob, relative to the gear blank, areemployable and are dependent upon the type of gear to be cut. The hobfeed directions include axial, oblique, infeed (or plunge) andtangential. Generally, the hob is fed into contact with the gear blankas opposed to the gear blank being fed into contact with the hob. Axialhob feeding includes the hob being fed into the gear blank along a paththat is parallel to the axis of rotation of the gear blank. In obliquehobbing, the hob path is at an angle relative to the axis of rotation ofthe gear blank. In this manner, the cutting action is distributed alongan increased length of the hob as it is fed across the gear blank. Ininfeed hobbing, the hob is fed radially inward into the gear blank. Withtangential hobbing, the hob is fed tangentially across the gear blank.

Besides rough forming of gear teeth, other forming processes may berequired for a particular gear design. For example, typical gear designsdictate that a chamfer be formed on each side of the individual gearteeth. To achieve this, a second roughing process is required usingadditional tools and machines. Generally, a chamfering tool is used andincludes a circumferential face having a set of mating gear teethrecessed between chamfer forming faces. The rough gear and tool arepressed into engagement with one another, wherein the rough gear blankmeshes with the mating gear teeth of the chamfering tool and both thetool and the rough gear rotate in unison. As the rough gear andchamfering tool rotate, the chamfer forming faces displace material ateach side of the individual gear teeth, thus forming a chamfer on eachside of the individual gear teeth.

Having thus formed the chamfers, the displaced material must be removedfrom the rough gear in a process known as deburring. Deburring of therough gear is typically achieved using a third process that implements athird tool for cutting away the displaced material. It is, however,known in the art to combine the chamfer forming and deburring tools. Asingle chamfer/debur tool is constructed similarly as described abovefor the chamfer tool, however, further includes cutters associated withthe chamfer forming faces. The cutters remove the displaced materialimmediately after the corresponding forming face forms the chamfer.

To finish the gear, a finishing process is performed. Gear finishingprocesses are used for improving accuracy and uniformity of the gearteeth. The degree of accuracy and, thus, the finishing process requiredis dependent upon the functional requirements of the gear.

Gear shaving is the most commonly used method of finishing gear teethprior to hardening. Gear shaving is a cutting process, whereby materialis removed from the profiles of each gear tooth by a cutter. The cuttermay vary in form, typically resembling a gear or rack depending uponwhether a rotary or a rack gear shaving method is used.

Typical gear production lines include a series of machines forperforming each of the above-described processes. As such, each machinerequires an initial capital investment cost and the other associatedcosts described above. Furthermore, general production cycle-time of aproduction line, having multiple machines, includes transfer timebetween machines. Key elements of manufacturing costs include, but arenot limited to, the number of machines required, the number of processesrequired, the set-up time between the processes and the overallcycle-time of each work-piece. As manufacturers seek to improve overalloperational costs reduction in any one of these areas is sought.Manufacturers seek to reduce the amount of machines required forproduction, thereby reducing capital and maintenance costs, as well asreducing the cycle-time for producing each component, thus increasingthe efficiency of the complete process.

A majority of state-of-the-art machine tools are computer numericallycontrolled machines or “CNC” machines. Such machines use computercontrol for both machine operation and set-up. Computers further enablea series of machines that perform separate functions to work in concertto perform several operations on a work piece and to mass produce finalproducts. Each machine, however, must be independently programmed by anoperator prior to processing a new work piece design. Because eachmachine is independently programmed, set-up time and thus, overallmanufacture time is less efficient than desired. As a result, overallmanufacture cost and product cost is higher than desired.

Therefore, it is desirable in the industry to provide improved machineryfor producing components, such as gears. The improved machinery shouldlimit the need for additional, supporting machines, reduce the overallcapital investment and maintenance costs, as well as reduce the cycletime of component manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a gear manufacturing apparatus accordingto the principles of the present invention;

FIG. 2 is a plan view of a combination hob/shave tool of the gearmanufacturing apparatus of FIG. 1; and

FIG. 3 is a plan view of a combination chamfer/debur tool of the gearmanufacturing apparatus of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With particular reference to FIG. 1, an exemplary embodiment of afour-process manufacturing apparatus 10 (the apparatus) is shown. Theapparatus 10 of the exemplary embodiment is provided for the manufactureof gears. However, it should be noted that the apparatus 10 ispreferably variable for manufacture of any one of a number ofalternative components. The apparatus 10 and its related components,described in detail below, are preferably CNC controlled by any one of anumber of controllers (not shown) commonly known in the art. Thecontroller is programmable for manufacturing a variety of componentsand/or component designs. It is foreseen that the controller is alsoprogrammable to simultaneously control operation of the rectilinearmovement of the various stocks described herein.

The apparatus 10 includes a generally rectangular, solid metal base 12providing a solid support structure for the various apparatus componentsdescribed herein. First and second stocks 14, 16 are included and areeach slidably engaged with the base 12. A third stock 18 slidablyengages the first stock 14. A fourth stock 20 is rotatably supported bythe third stock 18 and operatively supports a combination hob/shave tool22. A fifth stock 24 is positioned between the first and second stocks14, 16 and operatively supports a combination chamfer/debur tool 26. Thesecond stock 16 includes a retention device 28 for operably retaining awork-piece (not shown) during manufacture. Rectilinear movement of thevarious sliding stocks described above is achieved by respective drivemotors that act through speed reducing gearing and recirculating ballscrew drives.

The base 12 includes a top surface 30, to which the first and secondstocks 14, 16 are slidably interfaced. The first stock 14 is slidablealong a first axis X that runs along the length of the base 12. Thesecond stock 16 is slidable along a second axis Y that is generallyperpendicular to the first axis X, running across the width of the base12. The base 12 includes a first pair of rails 32 disposed along alength of and extending upward from the top surface 30. The first pairof rails 32 slidably engages a corresponding pair of rails 34 disposedon a bottom surface of the first stock 14. Rectilinear movement of thefirst stock 14 is imparted by a drive motor 36 acting through a gearreduction unit 38 and a ball screw 40. The drive motor 36 iscontrollable for selectively sliding and locating the first stock 14along the axis X. The base 12 further includes a second pair of rails 42disposed across a width of and extending upward from the top surface 30.The second pair of rails 42 slidably engages a corresponding pair ofrails 44 disposed on a bottom surface of the second stock 16.Rectilinear movement of the second stock 16 is imparted by a drive motor46 acting through a gear reduction unit 48 and a ball screw 50. Thedrive motor 46 is controllable for selectively sliding and locating thesecond stock 16 along the axis Y.

The first stock 14 includes a front face 52 to which the third stock 18is slidably attached. The front face 52 of the first stock 14 includes apair of rails 54 extending therefrom that slidably engage acorresponding pair of rails 56 disposed on a back face of the thirdstock 18. The third stock 18 is slidable along a vertical axis Z of thefront face 52. A drive motor (not shown) acting through a gear reductionunit (not shown) and ball screw (not shown) are provided for selectivelysliding and locating the third stock 18 along the axis Z, relative tothe second stock 16.

The third stock 18 further includes a front face 64, to which the fourthstock 20 is rotatably attached. The fourth stock 20 is selectivelyrotatable about a rotational axis A and includes first and second arms66 a, 66 b extending therefrom, for operably retaining the combinationhob/shave tool 22 therebetween. A positioning motor (not shown) isprovided for rotationally positioning the fourth stock 20 about therotational axis A. The hob/shave tool 22 is rotatably driven, by a drivemotor 70, about an axis B that is generally parallel to the front face64 of the third stock 18 and is initially generally perpendicular to theaxis A. The rotational position of the fourth stock 20 and the lateralposition of the third stock 18 are controlled by the controller.

With reference to FIG. 2, the hob/shave tool 22 includes a hob 80 and ashaver 82 affixed to one another. It should be noted, however thatdetachment of the hob 80 and shaver 82 is anticipated, whereby a portionof the hob/shave tool 22 may be replaced if worn before the otherportion. The hob 80 is generally cylindrical in shape and includes aplurality of hob teeth 84 radially extending from a circumferentialsurface. The hob teeth 84 follow a generally helical path along thelength of the hob 80. The shaver 82 is generally gear shaped including aplurality of gear teeth 86 and a clearance hole (not shown) through thebase of each tooth 86. The gear teeth 86 are serrated to provide aseries of cutting edges 90. The serrations extend from the tip of thetooth 86 into the clearance hole. The clearance holes provide channelsfor the flow of cutting fluid and material as the shaver operates.

With reference to FIG. 3, the chamfer/debur tool 26 is operativelysupported by the fifth stock 24 and is rotatably driven by a drive motor(not shown) through a gear unit (not shown). With reference to FIG. 3,the chamfer/debur tool 26 is a generally gear shaped tool having aseries of gear teeth 96 extending radially from an outsidecircumferential surface. At the ends of each of the gear teeth 96 islocated a chamfer surface 98 that serves to displace material at theends of gear teeth formed on the work-piece thereby producing a chamfer.Positioned adjacent each chamfer surface 98 is a cutting edge 100 thatcuts away the displaced material for deburring the chamfer of the gearteeth.

As mentioned previously, the second stock 16 includes the retentiondevice 28 for selectively holding a work-piece. It is foreseen that thework-piece may be either manually loaded, by an operator, oralternatively, an automated loading system (not shown) may be includedfor loading the work-piece into the apparatus 10. The work-piece is heldby the retention device 28 such that it is freely rotatable about arotational axis C. The rotational axis C is generally parallel to thefront face 64 of the third stock 18 and perpendicular to the top surface30 of the base 12. Rotation of the work-piece about the axis C is drivenby the tools as described in further detail herein. It is also foreseenthat the second stock 16 is rotatable about an axis D. The rotationalposition of the second stock 16 is controlled by a positioning motor(not shown).

With reference to the Figures, a method of manufacturing a gear and thecorresponding operation of the apparatus 10 will be described in detail.Manufacturing of a gear includes the steps of: loading a gear blank(work-piece), hobbing rough gear teeth into the work-piece, chamferingand deburring the rough gear-teeth, finishing the gear teeth viashaving, and unloading the finished work-piece.

Initially, a work-piece, in the form of a cylindrical gear blank, isloaded into the retention device 28 of the second stock 16. Once lockedin position, the controller initiates the hobbing step, whereby thehob/shave tool 22 is rotatably driven and fed into contact with thework-piece for forming rough gear teeth in the work-piece. The preferredfeeding method of the present invention is infeed or plunge. Thehob/shave tool 22 is infed via forward movement of the first stock 14along the axis X, relative to the second stock 16. As the hob/shave tool22 contacts a circumferential surface of the work-piece, the hob teeth84 begin cutting corresponding teeth into the circumferential surface.As the hob teeth 84 cut, the helical pattern of the gear teeth cause thework-piece to rotate about the axis C. In this manner, the gear teethare cut into the complete circumferential surface of the work-piece. Thenumber of revolutions of the hob/shave tool 22, and thus the work-piece,is dependent upon the number of threads of the hob/shave tool 22. Uponcompletion of rough gear tooth formation, the hob/shave tool 22 iswithdrawn through reverse movement of the first stock 14 along the axisX, relative to the second stock 16.

After the hob/shave tool 22 has been withdrawn, the chamfer/debur tool26 is brought into meshed engagement with the work-piece. Specifically,the gear teeth of the chamfer/debur tool 26 engage the rough gear teethof the work-piece. Initially, the chamfer/debur tool 26 is rotatablydriven in a first direction whereby the chamfer surfaces 98 displacematerial at both ends of the rough gear teeth and the displaced materialis cut away by the corresponding cutting edge 100. As the chamfer/deburtool 26 rotates, the meshed engagement with the work-piece causescorresponding rotation of the work-piece. The rotation of thechamfer/debur tool 26 then ceases and changes direction, rotating in asecond direction. In this manner, chamfers are formed at the ends ofeach of the rough gear teeth about the circumference of the work-pieceand excess material is cut away on both sides of each gear tooth. Uponcompletion of the chamfer/debur process, the chamfer/debur tool 26 iswithdrawn from the work-piece.

During operation of the chamfer/debur tool 26 on the work-piece, thefourth stock 20 is concurrently repositioned on the third stock 18 toprepare the hob/shave tool 22 for a subsequent shaving process. Thefourth stock 20 rotates approximately 90° on the front face 64 of thethird stock 18, whereby the rotational axis B is positioned generallyparallel to the rotational axis C and generally perpendicular to the topsurface 30 of the base 12. In this manner, the shaver 82 is properlyaligned for engagement with the work-piece. Concurrent repositioning ofthe fourth stock 20 helps to reduce overall cycle time of themanufacturing process.

Once the chamfer/debur tool 26 is completely withdrawn, the first stock14 again moves forward along the axis X and the third stock 18 isconcurrently adjusted on the Z axis whereby the shaver 82 of thehob/shave tool 22 is aligned for meshed engagement with the work-piece.The serrated teeth 86 of the shaver 82 engage the rough gear teeth ofthe work-piece. The hob/shave tool 22 is initially driven in a firstrotational direction by the fourth stock 20, whereby the work-piece iscorrespondingly caused to rotate, due to the meshed engagementtherebetween. Similar to the chamfer/debur tool 26, the shaver 82 stopsand rotates in a second direction opposite that of the first. This“reversal” process is repeated twice more for a total of six times,three in each direction. As the shaver 82 and work-piece rotatetogether, each of the serrated gear teeth 86 of the shaver 82 act uponthe rough gear teeth of the work-piece for finishing both sides of eachgear tooth of the work-piece. Upon completion of the shaving process,the hob/shave tool 22 is withdrawn and the finished gear is unloadedfrom the retention device 28.

As initially noted, the apparatus of the present invention includes fourmanufacturing processes. By performing four-processes, only a singlemachine need be purchased to produce a finished gear. Thus, significantsavings are realized in initial capital investment costs. Additionally,a single machine occupies less floor space, requires less maintenanceattention and less running costs, than multiple machines. Therefore,additional savings are achieved throughout the lifetime of the machine.Further, overall cycle-time is significantly reduced because a componentis only loaded and unloaded once and there is no transfer time presentbetween machines. The reduced cycle-time translates into further costsavings.

The description of the invention is merely exemplary in nature and,thus, variations that do not depart from the gist of the invention areintended to be within the scope of the invention. Such variations arenot to be regarded as a departure from the spirit and scope of theinvention.

1. A method of manufacturing a gear from a blank, comprising: providinga component holder for holding the blank; providing a rotatable toolretainer for operably supporting a combination hob and shave tool;forming gear teeth in the blank by rotatably driving said combinationhob and shave tool about a first axis; rotating said tool retainer suchthat said combination hob and shave tool is disposed on a second axisthat is generally perpendicular to said first axis; and shaving saidgear teeth by rotatably driving said combination hob and shave toolabout said second axis.
 2. The method of claim 1 wherein said rotatingof said tool retainer includes rotating said tool retainer about alongitudinal axis that is generally perpendicular to said first andsecond axes.
 3. The method of claim 2 wherein said forming of said gearteeth in the blank further includes translating said combination hob andshave tool in a first direction along said longitudinal axis and intoengagement with the blank.
 4. The method of claim 3 further comprisingtranslating said combination hob and shave tool in a second directionalong said longitudinal axis that is opposite said first direction andout of engagement with the blank prior to said rotating of said toolretainer.
 5. The method of claim 2 wherein said shaving of said gearteeth further includes translating said combination hob and shave toolin a first direction along said longitudinal axis and into engagementwith said gear teeth.
 6. The method of claim 1 further comprisingchamfering and deburring the blank by driving a combination chamfer anddebur tool into engagement with the blank substantiallycontemporaneously with said rotating of said tool retainer.
 7. Themethod of claim 1 further comprising translating said combination hoband shave tool along said second axis prior to said shaving of said gearteeth.
 8. The method of claim 1 further comprising providing a firststock supporting said tool retainer, wherein said first stock issupported on a base for sliding displacement along a longitudinal axisof the base.
 9. The method of claim 8 further comprising providing asecond stock supporting said component holder, wherein said second stockis supported on said base for sliding displacement along a lateral axisthat is generally perpendicular to said longitudinal axis.
 10. Themethod of claim 9 further comprising providing a third stock rotatablysupporting said tool retainer, wherein said third stock is supported onsaid first stock for sliding displacement along said second axis.
 11. Amethod of manufacturing a gear from a blank, comprising: providing acomponent holder for holding the blank; rotatably driving a combinationhob and shave tool about a first axis to thereby form gear teeth in theblank by translating said rotatable driven combination hob and shavetool in a first direction along a longitudinal axis and into engagementwith the blank; rotatably driving said combination hob and shave toolabout a second axis that is generally perpendicular to said first axisto thereby shave said gear teeth by translating said rotatably drivencombination hob and shave tool in said first direction along saidlongitudinal axis and into engagement with the blank.
 12. The method ofclaim 11 further comprising translating said combination hob and shavetool in a second direction along said longitudinal axis that is oppositeto said first direction prior to said rotatably driving said combinationhob and shave tool about said second axis.
 13. The method of claim 11further comprising providing a tool retainer rotatable about saidlongitudinal axis and operably supporting said combination hob and shavetool.
 14. The method of claim 13 further comprising rotating said toolretainer about said longitudinal axis such that said combination hob andshave tool is disposed on said second axis prior to said rotatablydriving said combination hob and shave tool about said second axis. 15.The method of claim 14 further comprising translating said tool retaineralong said second axis prior to said shaving of said gear teeth.
 16. Themethod of claim 14 further comprising chamfering and deburring the blankby rotatably driving a combination chamfer and debur tool intoengagement with the blank substantially contemporaneously with saidrotating of said tool retainer.
 17. The method of claim 13 furthercomprising providing a first stock supporting said tool retainer,wherein said first stock is supported on a base for sliding displacementalong said longitudinal axis.
 18. The method of claim 17 furthercomprising providing a second stock supporting said component holder,wherein said second stock is supported on said base for slidingdisplacement along a lateral axis that is generally perpendicular tosaid longitudinal axis.
 19. The method of claim 18 further comprisingproviding a third stock rotatably supporting said tool retainer, whereinsaid third stock is supported on said first stock for slidingdisplacement along said second axis.
 20. A method of manufacturing agear from a blank, comprising: providing a base; providing a componentholder for supporting the blank on said base; providing a first stockslidable on said base along a longitudinal axis; providing a toolretainer for retaining a combination hob and shave tool, wherein saidtool retainer is supported on said first stock for rotationaldisplacement about said longitudinal axis; rotatably driving saidcombination hob and shave tool about a first axis to thereby form roughgear teeth in the blank during a bobbing operation by translating saidfirst stock along said longitudinal axis such that a first portion ofsaid rotatably driven combination hob and shave tool engages the blank;rotating said tool retainer about said longitudinal axis such that saidcombination hob and shave tool is disposed on a second axis that isgenerally perpendicular to said first axis; chamfering and deburring theblank by engaging said rough gear teeth with said combination chamferand debur tool substantially contemporaneously with rotating said toolretainer; rotatably driving said combination hob and shave tool aboutsaid second axis to thereby shave the blank during a shaving operationby translating said tool retainer along said longitudinal axis such thata second portion of said rotatably driven combination hob and shave toolengages said blank.